It is known that vibration of the surrounding structures caused by turbulent blood flow in a partially occluded vessel may produce sounds which are significantly attenuated at body surfaces.
Turbulent blood flow is evidenced by non-uniform spatial distribution of blood flow sound phase coherence. Absent turbulence, blood flow sound phase coherence is generally uniform.
Various techniques for acoustic detection of turbulent blood flow are known. See, e.g., Lees, et al., (1970) Proceedings of the National Academy of Sciences 67(2):935-942; Semmlow, et al., (1982) "Non-Invasive Diagnosis of Coronary Artery Disease by Enhanced Coronary Phonocardiography", Abstract, IEEE Frontiers of Engineering in Health Care, pp. 181-185; Semmlow, et al., (1983) IEEE Transactions on Biomedical Engineering, BME-30(2):136-139; Wang, et al., (1990) IEEE Transactions on Biomedical Engineering, 37(11):1087-1094; Semmlow, et al., (1990) IEEE Engineering in Medicine and Biology Magazine, pp. 33-36; Akay, et al., (1992(1)) IEEE Transactions on Biomedical Engineering, 39(2):176-183; Akay, et al., (1992(2)) Medical & Biological Engineering & Computing, 30:147-154; Akay, et al., (1993(1)) IEEE Transactions on Biomedical Engineering, 40(6):571-578; Akay, et al., (1993(2)) Annals of Biomedical Engineering, 21:9-17; Verburg, J. (1983) Adv. Cardiovasc. Phys. 5(Part III):84-103.